The invention relates to a method for monitoring the adjustment movement of a component which is driven by a drive device and is adjustable in a translatory or rotary fashion, in particular a method for determining the force with which a drive device adjusts a component or traps an object which is located in the adjustment travel of the component.
DE 198 40 164 A1 discloses a method for adjusting a component which can be moved in a translatory fashion between two positions and in which the instantaneous force effect on the component which can be moved in a translatory fashion from the period length of a drive motor which is part of a drive device which adjusts the component which can be adjusted in a translatory fashion is calculated from force change values which are calculated from changes in the rotational speed of the drive motor, and from which summed force change values and force change values which have been weighted by means of equation systems which have been created by means of a mathematical model of the entire adjustment device including the drive are determined, said force change values depending exclusively on the behavior of the drive motor. The instantaneous force effect on the component which can be moved in a translatory fashion is used as a criterion for the switching off or reversal of the drive motor, the value of an upper threshold value being used instead of the value for the change in rotational speed in the calculation of the force change values for each value for a change in rotational speed which exceeds said upper threshold value.
In order to limit the number of physical variables to be sensed and the frequency of the samplings of the physical variables, the period length of the rotations of the drive motor is sensed by means of a magnet wheel and two Hall sensors. Fine resolution monitoring of the trapping prevention criteria is aimed at on the basis of the sensed period length in conjunction with various parameters sensed empirically or by measuring means, by extrapolating the sensed period length.
For this purpose, in order to determine the instantaneous force effect on the component which is moved in a translatory fashion, the measured values of the period length which are available only on a period basis are extrapolated, the parameters which are used during the extrapolation formula modulating the entire system of the drive device and being determined by means of the spring stiffness, attenuation and friction values of the entire system. As a result, spectral components of the period time profile which originate from vibrations are evaluated more weakly than those which originate from a case of trapping. From the estimated values which are determined for the period length in this way, the change in rotational speed is then estimated at a time with respect to the preceding time using a motor voltage filter and a displacement profile filter in order to eliminate the influences of the motor voltage and the position of the movable vehicle component on the motor speed.
The to eliminate the motor voltage and position of the component which can be moved in a translatory fashion on the motor speed model, inter alia, the dynamic behavior of the drive motor when there are changes in voltage. A further correction is performed by the estimated changes in rotational speed being compared with a fixed, chronologically constant lower limit. If the estimated changes in rotational speed exceed this lower limit, they are multiplied by a proportionality factor which represents the steepness of the motor characteristic curve of the drive motor.
DE 40 20 351 C2 discloses a method for controlling a window pane of a motor vehicle in which a correction method is applied in order to derive a trapping prevention criterion which is intended to prevent excessively early response of a trapping prevention device. For this purpose, a first sensor device supplies control electronics with signals which are associated in terms of their origin with the window pane and the drive device which moves the window pane, these signals being the voltage of the onboard electrical system, the window lifter speed, the torque of the drive, the weight of the window pane etc., while a second sensor element supplies the control electronics with signals which are not associated in terms of their origin with the window pane and the drive device, specifically with acceleration forces which act on the vehicle bodywork. In order to prevent the trapping prevention device being incorrectly switched off or reversed, the signals of the second sensor element are used as a basic level and the signals of the first sensor device are evaluated in terms of safety criteria.
In the known method, use is made of a relative detection of a vehicle body by means of a rise in the period length, that is to say the force changes at successive time intervals are compared with one another, as a result of which the run up of the component which can be moved in a translatory fashion can be differentiated only with difficulty from the trapping of an object in the adjustment travel of the component which can be moved in a translatory fashion.
When there are jumps in voltage in the onboard electrical system of a motor vehicle and when sections of poor road are traveled over, the known methods bring about overcompensation of the interference variables, which leads to high offsets with very high forces so that the permissible trapping forces are exceeded. A further disadvantage of the known methods is that the force acting on the component which can be moved in a translatory fashion can be detected only when there is a rise in the period length, which leads to high forces when there is a degression in the period length, that is to say when the period length decreases, for example owing to ease of movement of the component which can be moved in a translatory fashion, which also leads to increased trapping forces.
Changes in the profile of the adjustment travel of the component which can be moved in a translatory fashion which are due to ageing and wear are compensated in the known method by parameter changes, which entails readjustment of the control algorithm and a correspondingly complex control method.
Finally, the known methods are dependent on the selection of a specific number of different parameters which are decisive for the switching off and reversing of the component which can be moved in a translatory fashion, which entails corresponding complexity of sensor systems and control equipment when there is a relatively large number of parameters.
DE 101 96 629 T1 discloses the use of a neural network in a sensor system for a driven closing system and a method for preventing a driven closing system from closing according to requirements, in which method the sensor system detects objects by means of a proximity sensor before trapping occurs. However, the problems which occur with the known methods which are specified above relate to the sensing of signals of the drive device which makes evaluation and fault correction particularly difficult owing to the variables which influence one another.